I think that this is certainly quite the task, but i’d say just read the book, research what you like, make sure it is papered, no flaws. and you should leave happy with something nice.
first blade shouldn’t be a masterpiece, something you enjoy, to learn from and later you come back for something really grand.
1. Research, read books gain knowledge
2. Learn how to identify flaws, etc
3. Ensure the blade has papers, NBTHK
4. Most importantly make sure you enjoy it, I understand the excitement, but don’t buy something for the sake of buying something, there is always another time.
There is a list of good dealers somewhere in the forums i’m sure, but AoiArt is in central Tokyo in Shibuya, Eirakudo is another good one, most of their inventory is Koto which seems to be what you like. And far, far more dealers though those are what are on my mind now.
Have fun with it sounds like quite a quest, if you do find something make sure to show us! look forward to it!
Wish you well, safe travels.